PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
April 2017
265
of the area. Birdseye’s commission erected 1,028 pillars and
completed its work between 1933 and 1936. The award of the
Special Boundary Tribunal was based on the principle of u
ti
possidetis
as of 1821. Thus, the award referred to the territory
under the administrative control of Guatemala and Honduras
at the time of their independence from Spain. Furthermore,
El Salvador, Guatemala, and Honduras signed a protocol on
26 March 1936 accepting Cerro Monte Cristo as the tri-point
of the boundaries of the three states. A fascinating aspect
of the Guatemala-Honduras boundary is that part of the
boundary is “established on the right banks of the Tinto and
Motagua rivers at mean high water mark, and in the event of
changes in these streams in the course of time, whether due
to accretion, erosion or avulsion, the boundary shall follow
the mean high water mark upon the
actual right banks of
both rivers
.” (Emphasis added). Boundaries commonly do
not change with avulsions. Apparently, this was intended to
avoid future squabbles.
The Ocotepeque Datum of 1935 was established at Base
Norte where
f
o
= 14° 26´ 20.168˝ North,
l
o
= 89° 11´ 33.964˝
West of Greenwich, and H
o
= 806.99 meters above mean sea
level. The defining geodetic azimuth to Base Sur is: α
o
= 235°
54´ 21.790˝, and the ellipsoid of reference is the Clarke 1866
where a = 6,378,206.4 meters and
1
/
f
= 294.9786982. The
corresponding astronomic observations at that mountainous
location are: Φ
o
= 14° 26´ 13.73˝ North (±0.07˝), Λ
o
= 89°
11´ 39.67˝ West (±0.045˝), and the defining astronomic
azimuth to Base Sur is: α
o
= 235° 54´ 20.37˝ (±0.28˝). The
difference between these two sets of coordinates is due to
the local gravimetric deflection of the vertical. There was no
Grid system associated with this Datum, although that’s not
surprising since Mr. Birdseye was with the USC&GS. Their
custom was to compute their chains of quadrilaterals in
geodetic coordinates.
Nothing much happened (geodetically) anywhere in
Central America during World War II. After the war, the U.S.
Army Map Service (AMS) established the Inter American
Geodetic Survey (IAGS) headquartered in the U.S. Canal
Zone of Panamá. Co-operative agreements negotiated with
most countries in Latin America included the Republic of
Honduras. In November of 1946, the Comisión Geográfica
Nacional (CGN) was established under the Secretary of
War to satisfy the conditions of agreement with the IAGS.
The previous geodetic boundary work of the USC&GS was
integrated into the new IAGS observations along with the
chains of quadrilaterals observed in Guatemala (with the
IAGS). With connections to the classical triangulation in
Mexico, the North American Datum of 1927 (NAD 27) was
eventually introduced to the Republic of Honduras. Of
particular convenience was the fact that the Ocotepeque
Datum of 1935 was referenced to the same ellipsoid! (That
was courtesy of the USC&GS.)
The IAGSmethod of computing chains of quadrilaterals was
the “Army way” of doing things. That way was different from
the USC&GS because AMS was concerned with unifying the
mish-mash of Datums in post-war Europe. The planning and
design for that spectacular computational chore in Europe
was ultimately accomplished with a conformal projection and
Grid. The complexity of existing systems in the Americas was
much simpler, but the Topographic Engineers of AMS were
trained according to the “Army way.” That way consisted
of computing classical triangulation on a conformal Grid.
Central American countries, with the exception of Belize,
are greater in east-west extent than in north-south extent.
Therefore, the Lambert Conformal Conic projection was used
as the basis of all IAGS-developed Grid systems in Central
America for triangulation computations and the published
“Trig Lists” of coordinates.
The Honduras Lambert Conformal Grid (1946 - present)
on the Ocotepeque Datum of 1935 covers two secant zones,
Norte and Sud. Both zones use the same Central Meridian
(
l
o
) = 86° 10´ 00˝ West of Greenwich and False Easting of 500
km. Zone Norte has a Latitude of Origin (
f
o
) = 15° 30´ North,
the False Northing = 296,917.439 meters, and the scale factor
at origin (m
o
) = 0.999932730. Zone Sud has a Latitude of
Origin (
f
o
) = 13° 47´ North, the False Northing = 296,215.903
meters, and the scale factor at origin (m
o
) = 0.999951400.
In 1960, the Nicaragua-Honduras border dispute was
finally settled by the International Court of Justice (ICJ). The
determination was that the 1906 Award of the King of Spain
should be carried out based on the line of
uti possidetis
. In
1969, El Salvador and Honduras went to war over another
border dispute. This war involved six contested “bolsones”
(pockets) of land encompassing a total area of 436.9 square
kilometers, two islands (Meanguera and El Tigre) in the
Gulf of Fonseca, and the right of passage for Honduras to
the Pacific Ocean from its southern coast. A peace treaty
was signed in 1980, an arbitration agreement was signed in
1986, and the entire matter was resolved in 1993 after an ICJ
ruling the previous year.
Military mapping of Honduras at 1:50,000 scale (100%
coverage) and smaller is on theNAD27 and uses theUTMGrid
exclusively. An estimate of the transformation parameters
among the active datums in Honduras can be gleaned from
those pertinent to nearby Costa Rica. For example, (in Costa
Rica) from Ocotepeque 1935 to WGS 72: ΔX = –193.798 m, ΔY
= –37.807 m, ΔZ = +84.843 m. Furthermore, (in Costa Rica)
from Ocotepeque 1935 to NAD1927: ΔX = +205.435 m, ΔY =
–29.099 m, ΔZ = –292.202 m.
In Costa Rica, the fit of Ocotepeque Datum 1935 to WGS 72
is better than ±3 m; the fit of NAD 27 to WGS 72 is better than
±6 m. Considering the quality of classical geodetic work done
by the IAGS, the accuracy of these identical transformation
parameters applied in Honduras would probably be less than
double these values.
